选A正确! 考点: 固定句型 It+ be+adj+of/for sb to do sth 中的形容词与介词搭配. 当形容词表示主语的【品质、特点、属性等】,用of; 当形容词修饰不定式短语时,用for.例如: It is nice /kind of you to say so =You are nice/kind to say so It is important for us to learn a foreign language. 所给句子意思是: 我错了没有给他写信. 所以,应该表达为: It is wrong of me not to write him a letter.